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Volume 26,2021 Issue 5
Available online:February 22, 2023 DOI: 10.3878/j.issn.1006-9585.2022.22021
Abstract:Climate warming has led to more frequent and stronger extreme precipitation events in Central Asia (CA) in recent decades, which has seriously affected local socio-economic development and agricultural production. Based on the numerical simulations provided by the latest 14 coupled models of the Sixth Phase of Coupled Model Intercomparison Project (CMIP6), this study predicts and studies the spatial and temporal distribution characteristics of extreme precipitation over CA and its relationship with regional climate warming in the middle and late 21st century under two shared socio-economic paths (SSP2-4.5 and SSP5-8.5). The results show that most CMIP6 models can basically simulate the spatial distribution characteristics of observed precipitation climate states for 1979-2018, but the model simulations underestimate the observations in the southwest and southeast of CA, and overestimate the observations in the north and Central South of CA. Compared with the historical period (1981-2010), the precipitation intensity at the end of the 21st century (2071-2100) increased by 0.54 mm/10a and 2.4 mm/10a under the scenarios of SSP2-4.5 and SSP5-8.5 respectively, while the frequency of extreme precipitation events increased by 5-7% and 6-10% respectively, especially in the high-altitude mountains in central and southern regions. The signal-to-noise ratio (SNR) of the predicted precipitation intensity and frequency in northeast Central Asia to the north of The Tianshan Mountains is more reliable. Climate warming has an obvious regulatory effect on the frequency of extreme precipitation events in CA in the future. For the temperature rises by 1K, the frequency of extreme heavy precipitation events increased by about 7and 9 days, while the maximum continuous dry days increased by 3 and 6 days, respectively.
Comparative study on the interannual and interdecadal changes of autumn and winter fog days in Southwest China
Available online:February 22, 2023 DOI: 10.3878/j.issn.1006-9585.2022.21049
Abstract:Fog is a severe weather hazard that greatly influences traffic and daily life with potentially heavy economic loss. Based on the 503 observed fog station data from 1958 to 2007, the temporal and spatial characteristics of fog days in autumn and winter were analyzed. It was found that the fog in autumn and winter occurs frequently over Southwest China. The annual average number of fog days in autumn and winter in Southwest China is more than 18 days, which is twice as many as that in eastern China in the same period. Moreover, there is a significant climate variability of fog days in autumn and winter in Southwest China, which is mainly reflected in the interannual and interdecadal scales, and there are significant differences in the meteorological conditions of fog days in different climate scales. On the interannual scale, the north wind anomaly in the middle and upper levels is more significant, which brings the cold air from the north to the southwest, causing the cold air anomaly in the middle and upper levels over the southwest. Moreover, due to the strong sinking movement over the region, the cold air in the upper levels is brought to the lower levels. At this time, because of the abnormally high temperature and humidity in the lower levels, the cold and warm air converges over Southwest China which is located in the north of the rain belt. In a result, the air is easily oversaturated, resulting the number of fog days increasing. On the interdecadal scale, the anomalous northerly wind in the lower level is more significant compared with the interannual scale, which brings the cold air in the lower level from the north to the southwest. This results in the decreasing of temperature, specific humidity and temperature dew point difference and further leads to the supersaturation of water vapor in the Southwest China because the temperature drops faster than the humidity. At the same time, the atmosphere is relatively stable, increasing the number of fog days.
Evolution characteristics of air quality and the impacts of biomass burning in foreign regions in Yunnan province in spring 2018-2021
Available online:September 30, 2022 DOI: 10.3878/j.issn.1006-9585.2022.22040
Abstract:Air pollution in Yunnan province in spring has been prominent in recent years, which becomes a key resistance for defending the blue sky. Evolution characteristics of air quality and the impacts of meteorological factors and biomass burning in foreign regions on air quality in Yunnan province during spring 2018-2021 were analyzed comprehensively, based on ground monitoring data and satellite remote sensing data. The results revealed that the non-attainment days had reached up to 262 days (including 6 heavy pollution days) in spring in the past four years, accounting for 91.3% for all cities and 96.8% in southern Yunnan of the whole year. For temporal distribution, the pollution was concentrated in mid-March to mid-April, and the heaviest was in 2019, followed by 2021 with decreasing excellent days and increasing fine days significantly. In 2020, the pollutant concentration was the lowest, but heavy pollution occurred for 6 days. For spatial distribution, the pollution in southern Yunnan was far higher than that in central and northern Yunnan, with the highest in Xishuangbannan accounting for 27% of all non-attainment days; but the ozone (O3) concentration is the highest in southwest and central Yunnan, with the highest in Pu’er. PM2.5 was the dominant primary pollutant during 2018-2021, but the proportion of O3 as the primary pollutan in 2018 and 2019 was a little higher than that of PM2.5. Generally, the relationship of PM2.5 and O3 shown a significantly positive synergistic effect, and high O3 levels promoted secondary generation of PM2.5. PM2.5 and O3 pollution was both associated with less precipitation and southwest wind; furthermore, combined with mid-high temperature and mid-low humidity, O3 pollution easily occurred, and PM2.5 pollution was related with mid-high temperature and mid-high humidity, and mid-high temperature and mid humidity caused synergistic pollution of O3 and PM2.5. Highest pollution in 2019 was associated with the highest temperature and the least precipitation. Air pollution in Yunnan was significantly positive correlated with the number of fire points in the day and 1-3 day lags, and the highest correlation for PM2.5 and O3 were 2 day lag and 1 day lag, respectively. Ultimately, in unfavorable meteorological conditions dominated by the southwestern monsoon, biomass burning in foreign regions, especially Myanmar in Indo-china Peninsula is the main source for air pollution in spring in Yunnan, which enhanced the secondary generation of air pollution. Thus, these results indicated that the focus of spring pollution control in Yunnan is to establish a perfect cross-border air pollution prevention and control mechanism and to strengthen the early warning of biomass burning in foreign regions under unfavorable weather conditions.
Available online:May 06, 2022 DOI: 10.3878/j.issn.1006-9585.2021.21165
Abstract:Using ERA data, the impact of upper jet disturbance kinetic energy on snowstorm on February 9, 2014, December 5, 2015, January 20, 2016 and January 24, 2018 were analyzed. In the process of snowstorm, it is usually accompanied by the existence of upper jet. On the one hand, the upper jet maintains its own existence, on the other hand, the vertical movement caused by it is conducive to the development of snowstorm. The vertical motion has two functions: one is that the vertical upward motion transports the low-level warm and moist air to the high-level to provide a continuous stream of water vapor for snowstorm; the other is that the vertical upward motion transports the disturbance kinetic energy in the jet downward to the low-level warm and cold air flow intersection area, which is also an area with wind shear，to provide disturbance kinetic energy for the local area, and further promote the occurrence and development of snowstorm.
Science and Technology Progress on Air Pollution Prevention and Control in the past ten years in China and Prospect
Available online:April 14, 2022 DOI: 10.3878/j.issn.1006-9585.2022.22015
Abstract:Facing the urgent requirements of air pollution prevention and control in China, the relevant national ministries and scientific research institutions have set up a number of scientific and technological programs to provide continuous support. Great progress has been made in theoretical research, monitoring methods, numerical simulation, and air pollution control and prevention technology, which provides a strong scientific and technological support for the practice of air pollution prevention and control in China and the successful conclusion of the battle of blue sky defense. This paper summarizes the deployment and progress of air pollution prevention and control science and technology in the past ten years, and analyzes the current situation and problems of air pollution prevention and control in China. Aiming at the “14th five-year plan”, suggestions on three aspects: basic research of air pollution, research and development of key technologies for pollution prevention and control, and application demonstrations are proposed. Focus on the coordination of PM2.5 and O3 control, pollution reduction and carbon reduction, we will further advance scientific and technological work on air pollution prevention and control, and provide key scientific and technological support for the building of a “Beautiful China” and the goal of carbon neutrality and carbon peak.
Abstract:Ammonia (NH3) is the most abundant alkaline gas in the atmosphere and the only source of particulate NH4+, playing an important role in the formation of secondary inorganic salts. NH3 can easily react with nitric acid (HNO3) and sulfuric acid (H2SO4) in the atmosphere to form secondary inorganic aerosols such as ammonium nitrate (NH4NO3) and ammonium sulfate ((NH4)2SO4). Therefore, the emission, transportation, and chemical transformation of NH3 have an important impact on the spatial and temporal distribution of global inorganic aerosols. In this paper, the atmospheric NH3 concentration observed by the Michelson interferometer (MIPAS) on ENVISAT satellite and the AIRS detector on Aqua satellite, as well as simulated by the global atmospheric chemistry climate model EMAC, are used to analyze the spatial distribution characteristics of atmospheric NH3 in East Asia from June to September in 2008-2011. The results show that the highest concentration of NH3 near the surface appears in northern India, and deep convection exists in the Bay of Bengal near northern India in summer. The upward transport column of NH3 appears over northern India and the Qinghai-Tibet Plateau. Although NH3 has a short lifetime, it can be transported to the upper troposphere and lower stratosphere (UTLS) in the deep convection region. During the Asian summer monsoon, the location of the anticyclone dominates the spatial distribution of NH3 in the UTLS. The location of the Asian summer monsoon anticyclone dominates the spatial distribution of NH3 in the UTLS area. The high concentration center of NH3 continues to exist in the anticyclone. The position of the high concentration center of NH3 corresponds well to the position of the center of the anticyclone, and there exist one or two NH3 high concentration centers, indicating that the change of the circulation pattern in the anticyclone has an important influence on the distribution of NH3 in the anticyclone.
Development of a Meteorology-Chemistry Two-Way Coupled Numerical Model (WRF-NAQPMS) and Its Application in a Severe Autumn Haze Simulation over the Beijing-Tianjin-Hebei Area, China
2014,19(2):153-163, DOI: 10.3878/j.issn.1006-9585.2014.13231
Abstract:An aerosol-optical module based on Mie scattering theory has been implemented in the Nested Air Quality Prediction Modeling System (NAQPMS), and a new coupler has been developed to deal with the interaction between the mesoscale meteorology model WRF (Weather Research and Forecasting Model) and NAQPMS. The one-way off-line and two-way coupled WRF-NAQPMS models are compared to simulate the severe haze in the Beijing-Tianjin-Hebei area from 27 September to 1 October 2013. The results show that the simulated meteorological elements and PM2.5 concentrations from the two-way coupled model with the aerosol direct radiation effect are more consistent with observations. During the haze period, the boundary layer meteorological elements change significantly because of the aerosol direct radiation effect over the Beijing-Tianjin-Hebei area: Incoming solar radiation is reduced by 25%, the 2-m temperature decreases by 1 ℃, the turbulent kinetic energy is reduced by 25%, the 10-m wind speed decreases by up to 0.2 m/s, and the planetary boundary layer (PBL) height is reduced by 25%. These changes make the atmospheric boundary layer more stable and further exacerbate air pollution over the areas where it is already severe, for example, the PM2.5 concentration increases by up to 30% over Shijiazhuang City. The analysis indicates that there is a positive feedback mechanism between haze and boundary layer meteorology, and the two-way coupled model incorporating this feedback is helpful for accurate simulation and forecasting of haze pollution processes.
2008,13(2):123-134, DOI: 10.3878/j.issn.1006-9585.2008.02.02
2010,15(4):337-353, DOI: 10.3878/j.issn.1006-9585.2010.04.01
2004,9(2):278-294, DOI: 10.3878/j.issn.1006-9585.2004.02.05
1999,4(1):98-103, DOI: 10.3878/j.issn.1006-9585.1999.01.21
2011,16(6):733-741, DOI: 10.3878/j.issn.1006-9585.2011.06.07
Abstract:A field performance of Doppler wind lidar Windcube (released by Leosphere Company) was conducted by Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP/CAS) and Leosphere Company (from France) at the 325 m meteorological tower site (a part of IAP, located between 3rd North Ring Road and 4th North Ring Road) from 11 December to 14 December 2007. The intercomparison of wind speed and wind direction obtained by Windcube and wind cup anemometers (fixed in the meteorological tower) shows that：1) 10 min averaged wind speed is highly consistent between two types of wind data at six matched levels (63 m, 80 m, 100 m, 120 m, 160 m, and 200 m), the correlation coefficients all equal or exceed 0.98. 2) 10 min averaged wind direction is calculated with the vector method, the correlation coefficients of averaged wind direction at the six levels are 0.99. 3) In comparison with domestic Doppler wind lidar, Windcube performs slightly better in wind speed measuring, and equally well in wind direction measuring. The intercomparison indicates that Windcube is a reliable and swift mobile system mea suring wind profile at low levels.
2009,14(1):69-76, DOI: 10.3878/j.issn.1006-9585.2009.01.08
Abstract:作为酸雨和细粒子的前体物，SO2对空气质量和人体健康乃至气候与环境的影响十分重要，特别是在不利于扩散的气象条件下，SO2可造成城市短时间严重污染事件。作者以2006年北京325 m气象塔15 m观测平台SO2观测数据为基础，结合同步气象资料分析研究发现：1) SO2浓度冬季高、夏季低；全年日均值为(22.5±22.1)×10-9，最大日均值能达到113×10-9。日变化呈现双峰型，峰值出现在北京时间08:00和22:00；并且季节差异明显，冬季浓度为夏季的4.5倍，采暖期为非采暖期的3.2倍。2) 风向、风速与SO2扩散和输送密切相关，高浓度SO2在东北、东、西方向上出现频率分别为25.8%、13.8%和11.8%；而西北、北方向上的风速越大对SO2清除效果越好。3)利用平均晴空指数划分采暖期阴霾天和晴天，发现阴霾天混合层高度与平均风速仅为(376±204) m和1.1 m·s-1，容易造成SO2累积。4) SO2污染过程呈现周期性的局地累积—清除特征，地形、静风和暖低压是造成北京2006年1月一次重污染事件的成因。
REN Guo-Yu, CHU Zi-Ying, ZHOU Ya-Qing, XU Ming-Zhi, WANG Ying, TANG Guo-Li, ZHAI Pan-Mao, SHAO Xue-Mei, ZHANG Ai-Ying, CHEN Zheng-Hong, GUO Jun, LIU Hong-Bin, ZHOU Jiang-Xing, ZHAO Zong-Ci, ZHANG Li, BAI Hu-Zhi, LIU Xue-Feng, TANG Hong-Yu
2005,10(4):701-716, DOI: 10.3878/j.issn.1006-9585.2005.04.01
Abstract:总结了"十五"攻关课题有关中国温度变化研究的若干进展.在资料质量控制和序列非均一性检验及订正的基础上,更新了中国地面近50年、100年和1 000年气温序列.研究表明,不论是近54年还是近100年全国年平均地面气温升高趋势一般比原来分析结果表明的要强,分别达到0.25℃/10 a和0.08℃/10 a.中国现代增暖最明显的地区包括东北、华北、西北和青藏高原北部,最显著的季节在冬季和春季.近50多年中国近地面气候变暖主要是平均最低气温明显上升的结果,全国范围内极端最低气温也显著升高,而极端最高气温升高不多.中国与温度相关的极端气候事件强度和频率一般呈降低趋势或稳定态势.研究发现,城市化因素对中国地面平均气温记录具有显著影响,但在现有的全国和区域平均温度变化分析中一般没有考虑,因此需要在将来的研究中给予密切关注.在增温明显的华北地区,1961～2000年间城市化引起的年平均气温增加值达到0.44℃,占全部增温的38%,城市化引起的增温速率为0.11℃/10 a.中国其他地区的增温趋势中也或多或少反映出增强的城市热岛效应影响.20世纪60年代初以来中国对流层中下层温度变化趋势不明显,仅为0.05℃/10 a,比地面气温变化小一个量级;对流层上层和平流层底层年平均温度呈明显下降趋势,变化速率分别为-0.17℃/10 a和-0.22℃/10 a;整个对流层平均温度呈微弱下降趋势.中国对流层温度与地面气温变化趋势存在明显的差异,但这种差异在20世纪80年代初以后趋于减小.近千年来中国地面气温变化史上可能确存在"中世纪温暖期"和"小冰期"等特征性气候阶段,但"中世纪温暖期"的温暖程度似乎没有过去认为的那样明显.从全国范围看,11世纪末和13世纪中的温暖程度可能均超过了20世纪30～40年代暖期,表明20世纪的增暖可能并非史无前例.中国20世纪气候增暖的原因目前还不能给出明确回答.一些迹象表明,人类活动可能已经对中国的地面气温变化产生了影响,但太阳活动及气候系统内部的低频振动对现代气候变暖可能也具有重要影响.
2010,15(4):354-364, DOI: 10.3878/j.issn.1006-9585.2010.04.02
2006,11(1):14-32, DOI: 10.3878/j.issn.1006-9585.2006.01.02
Variations of the Sea Surface Temperature in the Offshore Area of China and Their Relationship with the East Asian Monsoon under the Global Warming
2011,16(1):94-104, DOI: 10.3878/j.issn.1006-9585.2011.01.09
Abstract:Based on the long time series of mean Sea Surface Temperature (SST) and high-resolution wind field reanalysis data such as HadISST and ERA-40 reanalysis data, the variations of the SST in the offshore area of China and their relationship with the East Asian Monsoon (EAM) in winter (December to the next February) and summer (June to August) are analyzed using the Empirical Orthogonal Function (EOF) and linear regression analysis methods. The results show that: 1) The SST in the offshore area of China in winter or summer exhibited significant interannual and interdecadal variations, and experienced a climate shift in the mid-1980s. The areas with the strongest increase in SST are located in the East China Sea (ECS) in winter and in the Yellow Sea in summer. The SST increased by 1.96°C in winter for the period of 1955-2005 and 1.10 °C in summer for the period of 1971-2006. 2）The EAM has displayed distinct interannual and interdecadal variations with a weakening trend since the end of the 1980s in winter, and since the end of the 1970s in summer. In addition, the linear regression analysis indicates the relationship of the SST to EAM in winter on interdecadal timescale is closer than that on interannual timescale. The interdecadal weakening trend of EAM in winter contributes to the rise in SST in the offshore areas of China, particularly significant in the ECS. Moreover, the related areas of winter or summer mean SST on the interannual timescale in the offshore area of China to the EAM are located in the South China Sea (SCS), and the relationship in winter is much more obvious than that in summer. It is found that the interannual variation of SST in the SCS has obvious relation to the anomalies of the meridional southward and northward winds over the SCS and zonal migration of the subtropical anticyclone over the western Pacific.
Variation Characteristics of the Sunshine Duration and Its Relationships with Temperature，Wind Speed，and Precipitation over Recent 59 Years in China
2011,16(3):389-398, DOI: 10.3878/j.issn.1006-9585.2011.03.14
Abstract:Using the data of sunshine duration, temperature, wind speed， and precipitation from 194 basic/reference stations over China from 1951 to 2009, according to the climatic division, the whole domain of China is classified into 11 climatic regions. The authors studied the changes in annual and seasonal trends of the sunshine duration by using linear trend analysis and Morlet wavelet analysis, and analyzed the characteristics between the sunshine duration and the temperature, the wind speed, and the precipitation. It was found that the annual sunshine duration showed a significant decreasing tendency during the recent 59 years with a decreasing rate of 36.9 h·(10 a)-1. The trend variations of the annual sunshine duration in 11 climatic regions were similar with that in the whole nation, only had the difference in degree. The sunshine duration of China changed from intensive to weak in 1981. There is an obvious 7－10-year periodic oscillation for the annual sunshine duration of China before the mid 1990s. The sunshine duration of the four seasons had a bigger decreasing amplitude in the coastal areas than in the inland areas, and in the South than in the North. There was a negative correlation between the annual sunshine duration and the temperature (correlation coefficient is -0.52), but a positive correlation between the annual sunshine duration and the wind speed (correlation coefficient is 0.76), and a negative correlation between the annual sunshine duration and the precipitation (correlation coefficient is -0.27). The first two correlation coefficients and the last correlation coefficient passed 99.9% and 95% confidence levels，respectively.
2002,7(2):209-219, DOI: 10.3878/j.issn.1006-9585.2002.02.08
The Mutual Response between Dynamical Core and Physical Parameterizations in Atmospheric General Circulation Models
2011,16(1):15-30, DOI: 10.3878/j.issn.1006-9585.2011.01.02
Abstract:A study of the interaction and mutual response between dynamical core and physical parameterizations by atmospheric general circulation models CAM3.1 and IAP AGCM4.0 is presented. Both the two models were integrated 60 d with ideal physics (Held-Suarez forcing) and with full physical package, respectively. The results show that the mutual responses between dynamical core and physical parameterizations are very different in the troposphere at low latitudes and high latitudes. In the tropical troposphere, the variability of temperature tendency due to dynamical core and that due to physical parameterizations are both large and have significant contributions to the variability of total temperature tendency, and they are in inverse correlation to compensate each other. In the polar middle and upper troposphere, the variability of total temperature tendency mainly relies on the tendency due to dynamical core, while the variation of temperature tendency due to physics is very slow, which can be seen as a stationary forcing. Unlike the tropical regions, there is a positive correlation between the temperature tendency due to dynamics and that due to physics in Polar regions. Moreover, the interactions and mutual responses between the individual physical parameterizations are also analyzed. The results show that the variation of temperature tendency due to moist process is the largest of all the physical parameterizations, and it contributes most to the total temperature tendency due to physics. The variation of temperature tendency due to long wave radiation is also large at high latitudes, while the variation of temperature tendency due to short wave radiation and that due to vertical diffusion are relatively small. There is a negative feedback between the cooling rate of long wave radiation and the heating rate of short wave radiation.
Simulation of Potential Vegetation Distribution and Estimation of Carbon Flux in China from 1981 to 1998 with LPJ Dynamic Global Vegetation Model
Abstract:The LPJ DGVM (Lund Potsdam Jena Dynamic Global Vegetation Model), which is a process based model, is used to simulate the vegetation distribution and estimate the interannual variation of net primary production (NPP), heterotrophic respiration (Rh) and net ecosystem production (NEP)in China from 1981 to 1998. It is shown that there are six main plant functional types (PFTs) besides the desert,that is tropical broadleaved evergreen tree, temperate broadleaved evergreen tree, temperate broadleaved summergreen tree, boreal needleleaved evergreen tree, boreal needleleaved summergreen tree and C3 perennial grass. In China, the total NPP varies between 2.91 Gt·a-1(C) (1982) and 3.37 Gt·a-1(C) (1990), increases by 0.025 Gt (C) average per year and has an increasing trend of 0.96%. The total Rh varies between 2.59 Gt·a-1(C) (1986) and 319 Gt·a-1(C)(1998), grows by 1.05% per year and by 0.025 Gt(C) per year. The linear trend of NPP and Rh for C3 perennial grass is more remarkable than those for other PFTs. The simulation of NEP is reasonable when the fire is brought in the model. Annual total NEP varies between -0.06 Gt·a-1(C)(1998)and 0.34 Gt·a-1(C)(1992). It is demonstrated that the terrestrial ecosystem is carbon sink in China. The above results are similar to those simulated by other models.
2010,15(5):541-550, DOI: 10.3878/j.issn.1006-9585.2010.05.02
Abstract:The Nested Air Quality Prediction Modeling System (NAQPMS) has been applied to the routine air quality forecast in Beijing during the Olympic Games. Monte Carlo method is used to analyze the uncertainty of ozone simulation of NAQPMS during the Olympic Games, from 8 to 24 Aug 2008. Latin hypercube sampling has been used for multi-variables sampling, and 50 ensemble runs have been made with 154 parameter uncertainties being considered together. By the temporal average, the most important parameter to the surface ozone output uncertainty in Beijing is the local precursor emissions during the day time. Other important factors include NO2 photolysis coefficient, wind direction, precursor emissions from the surrounding areas of Beijing, and vertical diffusion coefficient. The wind direction and precursor emissions from the surrounding areas of Beijing have the greatest impact on the uncertainty of daytime ozone simulation at higher levels (above about 150 m). The main uncertainty factors in ozone simulation at night are local NOx emissions and vertical diffusion coefficient. Given the predefined input uncertainties, the average uncertainty of ozone simulation is 19 ppb, ranging from 2 ppb to 49 ppb.
A Comparison of NCEP/NCAR, ERA-40 Reanalysis and Observational Data of Sensible Heat in Northwest China
2009,14(1):9-20, DOI: 10.3878/j.issn.1006-9585.2009.01.02
2008,13(1):75-83, DOI: 10.3878/j.issn.1006-9585.2008.01.10
2010,15(4):371-378, DOI: 10.3878/j.issn.1006-9585.2010.04.04
Decadal Variability of the Extreme Hot Event in China and Its Association with Atmospheric Circulations
2011,16(2):199-208, DOI: 10.3878/j.issn.1006-9585.2011.02.09
Abstract:Using observational daily maximum temperature of Chinese 181 stations for the period of 1957~2004, the spatio temporal features of the climatology and decadal variability of the extreme hot event (EHE) frequency, intensity, onset date (EHE OD), and termination date (EHE_TD) are investigated. The climatological analysis indicates that southeastern China and Xinjiang are the two major domains for the EHE, and eastern China is a region with a strong interannual variability. The EHE experienced strong decadal variability in the last 48 years. The variabilities of the frequency and intensity are consistent, and the variabilities of the EHE_OD and EHE_TD are similar. Based on the EHE spatio temporal feature, the whole China can be divided into four sub regions: Southern China, central China, eastern northern China, and Northwest China. The EHE frequency is high in the 1960s and the 1980s for southern China,in the 1960s and the 1990s for central China, and in the 1990s for northern China. Further, the atmospheric circulations which are responsible for the interannual and decadal variability of the EHE in the above four sub-regions are explored. It suggests that the circulations impacting on the interannual and decadal variability are consistent. For northern China, the major circulation is the overlying geopotential height anomaly at middle to upper levels. For southern and central China, the major circulations are the overlying geopotential height anomaly at middle to upper levels and temperature advection by the meridional wind at lower levels.
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Editor in chief: 李崇银